The spacecraft's main goals were to test such technologies as ion propulsion, autonomous optical navigation, a solar power concentration array, a miniature camera, and an imaging spectrometer during a flyby of the asteroid 9969 Braille.

A month after launch, on 24 November 1998, controllers fired the Deep Space 1's ion propulsion system (fueled by xenon gas) while the spacecraft was 4.8 million kilometers from Earth. The engine ran continuously for 14 days and demonstrated a specific impulse of 3,100 seconds, as much as ten times higher than possible with conventional chemical propellants.

DS1 passed by the near-Earth asteroid 9669 Braille at 04:46 UT on 29 July 1999 at a range of only 26 kilometers at a speed of 15.5 kilometers per second. It was the closest asteroid flyby at the time. Photographs taken and other data collected during the encounter were transmitted back to Earth in the following few days. DS1 found Braille to be 2.2 kilometers at its longest and 1 kilometer at its shortest.

Once the very successful primary mission was over on 18 September 1999, NASA formulated an extended mission. Originally, the plan had been to make DS1 fly by the dormant comet Wilson-Harrington in January 2001 and the comet Borrelly in September 2001, but the spacecraft's star tracker failed on 11 November 1999.

Mission planners revised the manifest to include a flyby that would not require a star-tracker- a single flyby of Borrelly in September 2001. By the end of 1999, the ion engine of DS1 had expended 22 kilograms of xenon to impart a total delta V of 1,300 meters per second. On its way to Borrelly, it set the record for the longest operating time for a propulsion system in space.

By 17 August 2000, the engine had been operating for 162 days as part of an eight-month run. On 22 September 2001, DS1 flew past the coma of comet Borrelly at 16.5 kilometers per second to obtain pictures and infrared spectra of the nucleus.

NASA terminated contact with DS1 on 18 December 2001, signaling the end to one of the more successful deep space missions in recent history.

Key Dates

24 Oct 1998: Launch

Status: Successful

Fast Facts

On its way to comet Borrelly, Deep Space 1 set a record at the time for the longest operating time on a spacecraft engine. (An ion engine similar to DS1's is shown at right.)

Deep Space 1 was dubbed the little spacecraft that could after completing a comet encounter without the use of a star tracker.

Because of Deep Space 1's technology testing, many future missions that would have been unaffordable or even impossible now are feasible.